1. Field of the Invention
The present invention relates to a device for assuring adequate emergency lighting, as well as sufficient visibility of alarm operating elements and instruction plates, in cars of passenger and freight elevators in case of power failure. Emergency lighting is necessary because, when there is a power failure, the elevator car can come to rest in a position where the passengers cannot leave it and remain trapped until the arrival of specialist assistance.
2. Discussion of the Prior Art
Most national and international elevator standards (as for example EN-81) require elevator installations to have emergency car lighting which switches on automatically if power failure occurs and which, being powered by a battery, guarantees a minimal level of lighting in the car for at least 1 hour.
U.S. Pat. No. 3,808,499 describes a battery-powered emergency supply unit for emergency lighting systems in elevator cars with functions such as charge voltage monitoring, charge level monitoring, charging rate control, power failure simulation, etc. Such, or similar, emergency lighting systems are nowadays built into practically all elevator cars.
Emergency lighting systems of the type described have a number of disadvantages. To keep their costs and installed weight low, their capacity is usually designed for the prescribed minimum power rating of 1 watt which must be delivered for a period of one hour. The resulting intensity of illumination is adequate to enable operation of certain devices such as an alarm button or intercom, but is often insufficient to prevent feelings of panic in passengers who are so disposed. Reading during the time of waiting until the elevator is released is practically impossible. In a fully occupied car, spreading of the light from the light source, which is usually in the form of a point, is usually hindered by passengers. Moreover, it can never be entirely ruled out that the emergency lighting device does not function when there is a power failure, especially since the emergency lamp can be relatively easily put out of action by vandals. In such a situation the passenger can neither read the relevant instruction plates, nor discern the alarm button or an intercom. Further disadvantages are that the status of these systems must be periodically checked, and that the batteries contained in them must be disposed of in a costly manner.
Accordingly, it is an object of the present invention to provide an emergency lighting device for elevator cars which fulfils the requirements specified in the regulations and does not have the disadvantages mentioned above.
According to the invention, this is achieved by affixing in the interior of the elevator cars in suitable positions phosphorescent materials in a suitable manner and in sufficient quantity. These are activated during operation of the elevator by the normal car lighting and, should this fail, the energy they have absorbed is emitted again in the form of visible light. This emission takes place in such a manner that the desired lighting effect is maintained for a period of more than an hour. An emergency lighting device according to the invention contains phosphorescent components with large area in the form of plastic foil parts, foils, or coats of paint (acrylic emulsion), which contain phosphorescent pigments as, for example, inorganic polycrystalline zinc sulfide.
By comparison with the prior art mentioned, this type of emergency lighting has considerable advantages.
Firstly, the phosphorescent sources of light with large surface achieve a much more even illumination of the elevator car than the usual 1-watt emergency lighting lamps in the form of a point. As already mentioned, this is especially the case when the car is fully occupied with passengers. Secondly, with modem fluorescent materials the rate of diminution of the light intensity is such that even after 3 hours enough light is emitted to prevent the occurrence of feelings of panic resulting from darkness. A third advantage is that emergency lighting of this type is extremely unsusceptible to faults, because it functions without wear and does not depend on an emergency power supply. The phosphorescent materials which are used permit a practically unlimited number of activation and emission cycles. No periodic check such as is required for emergency lighting with a lamp and an emergency power supply is required for this system. A further significant aspect is that a system of this type with phosphorescent components can be less easily put out of action by vandals than the emergency lighting lamps which are traditionally used.
There is separate inventive content in the phosphorescing construction of parts such as the emergency instruction plate, the alarm button, and the intercom. The advantage of such a construction is that these components are still legible or discernible even after several hours of power failure when the emission of light from the large surface of phosphorescent components serving as emergency lighting is no longer sufficient for this purpose.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.